1. The literature suggests that a large variety of stimuli control the accommodative mechanism. Two important stimuli appear to be blur, and perceived distance. An innovative system and methodology will be used to investigate the role that these stimuli play in effecting accommodation. 2. The normal "closed-loop" nature of the accommodative system (i.e. Changes in accommodation alter the amount of blur in order to clear the retinal image) tends to mask its characteristics. In the proposed research the feedback loop will be opened by feeding the signal from an infrared recording optometer ot a servo-system that controls the position of the stimulus. Changes in accommodation will therefore effect changes in the position of the stimulus, so that accommodation cannot reduce the amount of blur. Opening the feedback loop generally amplifies the response and should make it easier to identify the controlling stimuli and their relative importance. 3. To investigate the role that blur plays in stimulating accommodation, sine-wave gratings will be used as targets. Gratings covering a range of spatial frequencies will be moved toward and away from the subject in a sinusoidal manner at various temporal frequencies. To investigate the relative importance of perceived distance as a stimulus to accommodation, a disk-shaped target that changes size in a sinusoidal manner will be used. This target should lproduce the illusion of a sinusoidal change in the distance of the target. 4. This pilot study will lay the foundation for a comprehensive examination ofthe stimuli to accommodation. The research is foundational for a long-term clinical research project involving investigation of the accommodative system in the developing eye of ametropes, strabismics, and amblyopes.